diff --git a/.github/workflows/ci-v2.yaml b/.github/workflows/ci-v2.yaml
index 35102e8a..28794e71 100644
--- a/.github/workflows/ci-v2.yaml
+++ b/.github/workflows/ci-v2.yaml
@@ -17,10 +17,11 @@ jobs:
       working-directory: ./v2
 
     steps:
-    - name: Update base image and install Python2
+    - name: Update base image, intall Python2 and Python3
       run:  |
        sudo apt-get update
-       sudo apt-get install -y python2 
+       sudo apt-get install -y python2
+       sudo apt-get install -y python3
     - name: Set up Go
       uses: actions/setup-go@v2
       with:
@@ -51,6 +52,7 @@ jobs:
       working-directory: ${{env.working-directory}}
       run: |
         export APPENGINE_DEV_APPSERVER=$(which dev_appserver.py)
+        export CLOUDSDK_PYTHON="python3"
         go test -v -cover -race google.golang.org/appengine/v2/...
         # TestAPICallAllocations doesn't run under race detector.
         go test -v -cover google.golang.org/appengine/v2/internal/... -run TestAPICallAllocations
@@ -64,12 +66,13 @@ jobs:
         go-version: [ '1.11.x', '1.12.x']
     env:
       working-directory: ./v2
-    
+
     steps:
-    - name: Update base image and intall Python2
+    - name: Update base image, intall Python2 and Python3
       run:  |
        sudo apt-get update
-       sudo apt-get install -y python2     
+       sudo apt-get install -y python2
+       sudo apt-get install -y python3
     - name: Set up Go
       uses: actions/setup-go@v2
       with:
@@ -99,6 +102,7 @@ jobs:
       working-directory: ${{env.working-directory}}
       run: |
         export APPENGINE_DEV_APPSERVER=$(which dev_appserver.py)
+        export CLOUDSDK_PYTHON="python3"
         go test -v -cover -race google.golang.org/appengine/v2/...
         # TestAPICallAllocations doesn't run under race detector.
         go test -v -cover google.golang.org/appengine/v2/internal/... -run TestAPICallAllocations
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4d9e5c37..4b9f917c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -15,10 +15,12 @@ jobs:
         go-version: [ '1.11.x', '1.12.x', '1.13.x', '1.14.x', '1.15.x', '1.16.x', '1.18.x', '1.19.x', '1.20.x']
 
     steps:
-    - name: Update base image and intall Python2
+    - name: Update base image, intall Python2 and Python3
       run:  |
        sudo apt-get update
-       sudo apt-get install -y python2 
+       sudo apt-get install -y python2
+       sudo apt-get install -y python3
+       export CLOUDSDK_PYTHON="python3"
     - name: Set up Go
       uses: actions/setup-go@v2
       with:
@@ -47,10 +49,11 @@ jobs:
         GO111MODULE: on
       run: |
         export APPENGINE_DEV_APPSERVER=$(which dev_appserver.py)
+        export CLOUDSDK_PYTHON="python3"
         go test -v -cover -race google.golang.org/appengine/...
         # TestAPICallAllocations doesn't run under race detector.
         go test -v -cover google.golang.org/appengine/internal/... -run TestAPICallAllocations
-  
+
   test-gopath:
     runs-on: ubuntu-latest
     strategy:
@@ -60,10 +63,12 @@ jobs:
         go-version: [ '1.11.x', '1.12.x']
 
     steps:
-    - name: Update base image and intall Python2
+    - name: Update base image, intall Python2 and Python3
       run:  |
        sudo apt-get update
-       sudo apt-get install -y python2 
+       sudo apt-get install -y python2
+       sudo apt-get install -y python3
+       export CLOUDSDK_PYTHON="python3"
     - name: Set up Go
       uses: actions/setup-go@v2
       with:
@@ -91,6 +96,7 @@ jobs:
     - name: Test gopath
       run: |
         export APPENGINE_DEV_APPSERVER=$(which dev_appserver.py)
+        export CLOUDSDK_PYTHON="python3"
         go test -v -cover -race google.golang.org/appengine/...
         # TestAPICallAllocations doesn't run under race detector.
         go test -v -cover google.golang.org/appengine/internal/... -run TestAPICallAllocations
diff --git a/aetest/instance_vm.go b/aetest/instance_vm.go
index e1647fdb..1f36bbe6 100644
--- a/aetest/instance_vm.go
+++ b/aetest/instance_vm.go
@@ -145,7 +145,7 @@ func (i *instance) startChild() (err error) {
 			return err
 		}
 	}
-	executable := os.Getenv("APPENGINE_DEV_APPSERVER_BINARY")
+	executable := os.Getenv("APPENGINE_DEV_APPSERVER")
 	var appserverArgs []string
 	if len(executable) == 0 {
 		executable, err = findPython()
diff --git a/v2/aetest/instance.go b/v2/aetest/instance.go
index 994bec64..5ca59f64 100644
--- a/v2/aetest/instance.go
+++ b/v2/aetest/instance.go
@@ -167,7 +167,7 @@ func fileExists(path string) bool {
 }
 
 func findPython() (path string, err error) {
-	for _, name := range []string{"python2.7", "python"} {
+	for _, name := range []string{"python3"} {
 		path, err = exec.LookPath(name)
 		if err == nil {
 			return